Lecture 3/4 - Embryology Flashcards
why is it important to study embryology?
a. Logical framework for understanding adult anatomy
b. Provides information about many issues i.e. reproduction, contraception, stem cells etc
c. Informs about when things go wrong i.e. birth defects, cancer
Why are the early cell divisions called ‘cleavages?
Because it provides the large number of cells needed as building blocks for the embryo.
what are the two cell types of the blastocyst?
Trophoblasts and inner cell mass
what is gastrulation?
Gastrulation is the formation of the primitive streak (defines all major body axes) and formation of three germ layers. Basically, gives rise to distinct tissue in adults.
what is the function of the notochord?
It serves as a source of midline signals that pattern surrounding tissues and as a major skeletal element of the developing embryo.
from which germ layer does the neural tube form?
ectoderm
Where do neural crest cells come from?
originate in the ectoderm at the margins of the neural tube
what organs are formed by the ectoderm?
skin and nervous system (brain, spinal cord etc)
what drives embryonic folding?
Main force is differential growth of various tissues i.e. rapid growth of CNS and somites
name the three parts the mesoderm can be divided into
paraxial
intermediate
lateral
what gives rise to the urogenital system?
The intermediate mesoderm
- The urogenital system, is the kidneys, gonads and respective duct systems.
What structures does the paraxial mesoderm form?
The paraxial mesoderm = somatic mesoderm which forms somites, which will produce muscle, bone and dermis.
What are somites?
Segmental axial structures of vertebrate embryos that give rise to vertebral column, ribs, skeletal muscles and subcutaneous tissue.
what are dermatomes?
an area of skin innervated by a specific spinal nerve root.
What gives rise to the male and female reproductive tracts?
the intermediate mesoderm i.e. the gonads
What organs/structures develop from the lateral mesoderm?
Connective tissue of ventro-lateral body wall, bones of the limbs, heart and vascular, wall of gut
what germ layer forms the lungs?
Both the endoderm and mesoderm
describe how the stomach develops
a. Distal part of foregut, around middle of fourth week, slight dilation
b. Enlarges and broadens ventro-dorsally
c. Dorsal part grows faster than ventral part: greater curvature of stomach
d. While growing: rotation 90o clockwise
e. Ventral border (smaller curvature) moves to right, dorsal border (greater curvature) to left
f. Rotation superiorly bends duodenum into C-shape
how does the development of lungs start?
a. Ventral out-pocketing of endoderm = respiratory diverticulum –> forms trachea
b. Growths ventro-caudally
c. Bifurcation –> right and left primary tracheal buds –> will form bronchi
d. Next bifurcation: secondary bronchial buds (3 on right, 2 on left) –> lung lobes
e. Third bifurcation: tertiary bronchial buds –> bronchopulmonary segments
f. 14 more branching’s –> terminal bronchioles
What are the common elements in each of the pharyngeal arches?
a. Central cartilaginous skeletal element (derived from neural crest)
b. Striated muscle rudiment (derived from head mesoderm)
c. Arch-specific cranial nerve
d. Aortic arch artery (endothelial cells derived from mesoderm)
